I don't think that it's an aftermarket system, and there is a little red light behind the steering wheel that flashes when it's armed

 

Sounds like it's the dealer-installed accessory alarm, not the factory one in the EX. So I take it your Accord is an LX or DX? No flashing red light on the driver's door next to the lock-pin?

That being the case, go with Redbull's advice.